Compost mixing and aerating apparatus

ABSTRACT

An improved composting apparatus is provided which is particularly suited for use with straw-like materials. The composting apparatus includes a counter-rotating drum and paddle assembly which generates a plurality of air streams in which the composting material is entrained. The air streams rotate in a vortex like pattern within a chamber to mix and aerate the composting material. The composting apparatus is configurable for being driven sideways through fence gates and the like, and has an additional configuration for being towed without requiring a trailer.

This is a continuation-in-part of patent application Ser. No. 07/918,528filed Jul. 21, 1992 now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for mixing and aerating acomposting material, and particularly to an apparatus which is suitablefor use with a relatively light composting material such as straw.

Composting is a well-known method for converting solid wastes into auseful commodity. Composting of municipal waste and certain agriculturalwastes is currently practiced on a relatively large scale. Composting isbeing considered for disposal of additional agricultural wastes asenvironmental regulations render traditional disposal methodsunacceptable. In certain seed crop industries, grass seed for example,it has long been the practice to harvest the seed and then burn therelatively large volume of grass straw remaining. The grass seedindustry is now under pressure however to abandon large scale burning ofgrass straw due to its effect on air quality. Similar pressures arebeing exerted on other segments of the agricultural industry as well. Asa result, composting is receiving increasing attention as an alternativeto some of the traditional agricultural waste disposal methods.

Agricultural composting in general involves the partial decomposition ofa solid material by the action of aerobic bacteria. When practiced on asmall scale, it is relatively easy to maintain the aerobic conditionsrequired by the bacteria; it is much more difficult to do on a largerscale. Failure to maintain aerobic conditions throughout the compostingmaterial results in anaerobic decay of the material, which in thissituation is less efficient than aerobic decomposition, and normallyemits objectionable odors. This combination of undesirablecharacteristics provides strong incentive to maintain aerobic compostingconditions at all times.

There are known machines for physically mixing compost to maintainaerobic conditions. An example is U.S. Pat. No. 4,360,065 to Jenison etal. The Jenison cultivator comprises a horizontal rotating drum having aplurality of cultivator blades in two helical rows. As the drum isrotated, the blades travel edgewise through a pile of compostingmaterial to move the material sideways and pile it in a generallytriangular pile. The '065 patent further describes other compostingmachines such as the Scarab, sold by Scarab Manufacturing and Leasing,Inc. of White Deer, Tex. U.S. Pat. No. 3,369,797 to Cobey describes acompost turner and windrow forming machine having a transversely mountedrotating drum for the turning of compost piles and the redepositing ofthe turned up material in a windrow. Yet another composting apparatus isdescribed in U.S. Pat. No. 4,019,723 to Urbanczyk. The '723 patentdescribes a mobile composter for manure which moves a rotating drum overmasses of inoculated manure to flail it, mix it, cool it and aerate it,while moistening the particles as the same time. After being conditionedand moisturized, the material is formed into a pile by a rear outletopening. As with the Cobey composter, the flails mounted on the drum ofthe Urbanczyk machine travel edgewise through the composting materialfor flailing and mixing. U.S. Pat. No. 4,478,520 also to Cobey describesa compost turning machine which straddles a compost windrow whilecarrying a rotating drum for turning the composting material. The '520composter additionally has an adjuster auger system outboard of therotating drum to collect additional material and deposit it in the pathof the rotating drum. This is the Cobey machine referred to earlier.

These known composters are useful and effective for composting materialshaving a relatively high density, and which may require the addition ofmoisture for maintaining the proper composting conditions. However,known composting machines have proved unsuitable for use in compostingrelatively light, tough composting materials such as grass straw.Applicant has discovered that the unsuitability of known compostingmachines is due in part to their inability to throw light stringycomposting materials such as straw clear of the drum to prevent thestraw from fouling the drum paddles.

An additional limitation of known composting machines resides in thedifficulty of transporting them from one location to another. When usedin an agricultural setting, this problem is particularly acute. It maybe useful for instance, to compost agricultural waste in the field wherethe crop is grown. Where adjacent fields are separated by a fencetransporting known composting machines between fields often requiresdriving the machines short distances on public roads, or loading themachines onto transporters to deliver them to the adjacent fields.Commercial scale composters are so wide that they cannot be driventhrough standard gates and fences between adjoining fields. If thecomposting machine must be transported to a location other than anadjacent field the problem is further aggravated because of the width ofthe composting machine; it is simply too wide to be driven on a publichighway. It therefore must be loaded on a low-boy type trailer, andtowed to the next location.

A need therefore exists for a composting machine which is suitable foruse with relatively light agricultural waste products, or relativelylight composting materials of any sort, and which is readilytransportable between adjacent agricultural fields, or to a remotelocation.

SUMMARY OF THE INVENTION

It is a principal object of the present invention to provide a mixingand aerating machine for composting a wide variety of solid materials,including relatively light agricultural wastes such as grass straw.

It is another object of the invention to provide improved mixing andaeration of relatively light composting material by entraining thecomposting material in a stream of air for a sufficient time tothoroughly aerate the composting material.

It is another object of the invention to generate an air stream forentraining the composting material by rapidly rotating a drum assemblyhaving a plurality of blades protruding therefrom.

It is yet another object of the present invention to generate an airstream flowing in a generally vortex like pattern within a housing onthe underside of the composting machine for thoroughly mixing andaerating the composting material. These and other objects of the presentinvention will be described in the following specification and theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a front view of a composting apparatus according to thepresent invention.

FIG. 1A shows a front view of an alternative embodiment of the presentinvention.

FIG. 2 is a rear view of a composting apparatus according to the presentinvention.

FIG. 2A shows a rear view of an alternative embodiment of the presentinvention.

FIG. 3 is a left side view of the composting apparatus according to thepresent invention as shown in FIGS. 1 and 2.

FIG. 3A is a left side view of another embodiment of the compostingapparatus according to the present invention.

FIG. 4 is a right side view of the composting apparatus according to thepresent invention as shown in FIGS. 1 and 2.

FIG. 4A is a right side view of the composting apparatus according tothe present invention as shown in FIGS. 1A and 2A.

FIG. 4B is an enlarged view of the pivoting rear wheel assembly in itsextended position.

FIG. 5 is a top view of a composting apparatus according to the presentinvention configured for treating composting material.

FIG. 5A is a top view of an alternative embodiment of a compostingapparatus according to the present invention.

FIG. 6 is a top view of a composting apparatus according to the presentinvention configured for being transported by towing.

FIG. 7 is a front view of a composting apparatus shown in FIGS. 1 and 2configured for being transported by towing.

FIG. 7A is a front view of a composting apparatus shown in FIGS. 1A and2A configured for being transported by towing.

FIG. 7B is an enlarged view of the drum shaft bearing assembly.

FIG. 8 is a right side cross-sectional view of the drum and paddleassembly according to the present invention.

FIG. 9 is an enlarged sectional view of the center portion of the drumand paddle assembly, showing the counter-rotating vortex-like airstreamsgenerated when the assembly is rotated.

FIG. 9A is bottom view of an alternate drum and paddle assembly.

FIG. 10 is a top view of a right side paddle.

FIG. 11 is a top view of a center paddle.

FIG. 12 is a top view of a left side paddle.

FIG. 13 is a side view of a right side paddle showing the shear pinfeature, and showing the released paddle in phantom.

FIG. 14 is a front perspective view of a composter according to thepresent invention, having the drapes removed to expose the chamber anddrum assembly.

FIG. 15 shows the increased volume of a representative windrow formed bya composting apparatus according to the present invention.

FIG. 16 is a schematic diagram of the control circuit for slowing thespeed of the composter when the drum speed is reduced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIGS. 1 and 2, a first embodiment of a composteraccording to the present invention is shown generally at 10. A secondembodiment is shown in FIGS. 1A and 2A which differs in detail asdescribed below. Composter 10 includes frame 12 which is assembled fromladder-type left, right, and top subframes, 12a, 12b and 12crespectively. Frame 12 is supported at its front end by left and rightdrive wheels 14 and 16, and at the rear by left and right caster wheels18 and 19. Each wheel mounted on an axle which is journaled into asupporting frame assembly 40. Each rear caster wheel is mounted into itsrespective frame assembly 40 by a vertical shaft journaled into frameassembly 40 as shown in FIG. 3. Each rear caster wheel may be lockedinto a transverse position by locking pin assembly 19 when desired asdescribed below. Each frame assembly 40 includes an upright member 42slidably received within a complementary vertical sleeve 44 of amounting assembly 46. Frame assembly 40 may thereby be raised or loweredrelative to the ground on upright member 42 by actuation of hydrauliccylinder 43, allowing the ground clearance of composter 10 to be raisedor lowered during operation as more fully described below. Mountingbracket 46 is in turn pivotably mounted on frame 12 at brackets 48,allowing each frame assembly 40 and wheel to be pivoted by actuation ofhydraulic cylinder 45 for different modes of operation as describedbelow. An alternative design for the wheel frame assemblies 40 is shownin FIGS. 4A and 4B. Note that in the alternative frame assembly designfor drive wheels 14 and 16, frame assembly 40 does not pivot, but ratheris moved rearward by hydraulic cylinder 45 and raised up by hydrauliccylinder 43 to its stowed position.

As best seen by reference to FIG. 5, frame 12 includes upper deck 32 onwhich are mounted fuel tank 34, operator's cab 36, hydraulic oil tank37, engine 38, and hydraulic pumps 40, 42 and 44. As readily appreciatedby those skilled in the art, suitable auxiliary equipment for operationof the engine and drive components in dusty environments is alsoprovided, such as rotating self-cleaning screen 41 of the cooling systemof engine 38. Power for the operation of composter 10 is provided byhydraulic pumps 40, 42 and 44, which are driven by engine 38, preferablya 402 hp diesel engine such as Model 3406, manufactured by Caterpillar.Each hydraulic pump 40a and 40b delivers pressurized hydraulic fluid toeach of drum assembly drive motors 48a and 48b to reversibly driverotating drum and paddle assembly 22 from each end. Hydraulic pumps 42aand 42b deliver pressurized hydraulic fluid to left and right drivemotors 50 and 52 respectively. Pump 44a delivers pressurized fluid tohydraulic cylinders 43 for raising and lowering frame 12, while pump 44bprovides pressurized fluid for operating hydraulic cylinders 45, andhydraulic cylinder 54 for raising and lowering tail section 31. Left andright drive motors 50 and 52 are separately controllable by the operatorfor steering and for driving left and right drive wheels 14 and 16respectively through an appropriate drive assembly of a suitable designas could be readily determined by one skilled in the art.

In the preferred embodiment, a planetary gear assembly, Model No. W-2 asmanufactured by Fairfield is used on each the left side and right sidedrive wheel and motor assembly. The left side planetary drive assemblydiffers from that of the right side only in that it is rendered freewheeling for reasons described below by operation of an externalT-handle. Composter 10 is steerable and drivable forwardly, rearwardly,and sideways as described below by virtue of the fact that each drivewheel is drivable forwardly and rearwardly independently of the other byappropriate hydraulic controls of standard design and well-known tothose skilled in the art.

In an alternative four-wheel drive embodiment (FIG. 5A), left and rightcastor wheels 18 and 20 are replaced by left and right rear drive wheels15a and 15b and respective hydraulic drive motors 51 and 53.Corresponding controls as described above with reference to thetwo-wheel drive embodiment are provided to allow the operator to controlthe speed and direction of each of the four driven wheels.

While the present invention is not intended to be defined or limited byreference to any specific dimensions, in both prior art composters andthe present invention there is an efficiency of operation resulting fromincorporation of a relatively long drum assembly, 17 feet or more forexample. Accordingly, the overall width of the composter will be evengreater than the drum length, while the overall length of the frame ofthe composter is preferably no greater than 8'6". While providing moreefficient operation by requiring fewer passes to process a given amountof composting material, the overall width of prior art compostersprevents them from being driven through standard fence gates betweenadjacent fields, and requires that they be transported over public roadsby truck and trailers designed for transporting heavy equipment. Thepresent invention overcomes these limitations and cost disadvantages ofprior art composters by providing for the first time a composter whichmay be driven sideways under its own power through standard fence gatesor over public roads for short distances, and which may be towed forlonger distances over public roads when necessary. The means ofconfiguring the present invention for so doing will now be described byreference to FIG. 5 where it can be seen that each wheel is mounted on aframe assembly 40 which is movable between a first position foraccommodating forward and rearward travel of composter 10 during normaloperation, and a second transverse position for accommodating towing orsideways travel of the composter. Each frame assembly 40 is movedbetween the first and second positions by a dedicated hydraulic cylinder45, which is controlled by means of appropriate controls (not shown)from operator's cab 36.

Referring now to FIGS. 1 through 14, drum assembly 22 is mountedtransversely within chamber 24. Chamber 24 is an open-ended housingconsisting of a top wall 26, left and right side walls 28 and 30, andtail section 31 (FIG. 5). Front opening 25 is partially shrouded asshown in FIG. 1 by front drapes 33a-c. In the preferred embodiment,screened openings 23 are provided in left and right side walls 28 and 30ahead of drum 56 to permit additional air to be drawn into chamber 24during operation. (FIG. 3A). Tail section 31, essentially a rearwardlyextending projection of chamber 24, extends rearwardly from rear opening27. Tail section 31 may be described as a generally planar frame havingrearwardly and inwardly extending side members pivotally attached toframe 12 at one end, and to lateral member at their outer ends. Drapes39 are hung from each side member and the lateral member as best seen inFIG. 2. The drapes may be made from any suitable material. In thepresent embodiment, they are fabricated from grade 2 SBR in the form of1/2" thick conveyor belt material. Tail section 31 is pivotable byhydraulic cylinder 54 between a lowered operational position and araised stowed position for use during transport of the composter. Reardrapes 35 are hung from each side and the rear of tail section 31 andfrom angled frame members defining rear opening 27 as shown. Chamber 24serves to contain direct the air streams and composting material duringoperation of composter 10, and to reform the composting material into awindrow after mixing and aerating as more fully described below.

Drum assembly 22 is journaled at opposite ends in left and rightsubframes 12a and 12b. Hydraulic motors 48a and 48b are mounted on leftand right subframes 12a and 12b, and reversibly drive drum assembly 22by means of shafts 49a and 49b when supplied with pressurized hydraulicfluid from hydraulic pumps 40a and 40b as described above. Drum assembly22 includes drum 56, a hollow cylinder having closed ends, onto whichare welded shafts 57a and 57b (not shown). Shafts 57a and 57b arejournaled into frame 12, and drivably connected with drum assembly drivemotors 48 as described above. Each of shafts 57a and 57b are journaledinto its respective subframe by means of a four bolt flangetype taperedroller bearing 91 such as Model FB 900 manufactured by Browning Company.Each bearing 91 is fitted into a corresponding hole in left and rightsubframes 12a and 12b. A split ring collar 92 is fitted intocircumferential recesses 96 on each of shafts 57a and 57b, and bearsagainst the protruding rotating race 94 of the tapered roller bearing tocounteract spreading forces exerted on subframes 12 a and 12b. Drum 56thereby functions as a tension member in frame 12 counteractingspreading forces represented in FIG. 7A by force arrows 102a and 102b.This novel use of drum 56 as a tension member saves the weight ofadditional structural members which would otherwise be required tocounteract spreading forces on subframes 12a and 12b , and allows alower overall height which further accommodates towing the compostingapparatus on public highways.

Turning now to FIGS. 8-12, a plurality of left and right paddles 58 and60 respectively, and center paddles 62 are mounted on the outercylindrical surface of drum 56 as shown. In one embodiment, the paddlesare arranged in four evenly spaced helical rows along the length of thedrum, each row traversing 90° about the drum from one end to the other.In a second embodiment shown in FIG. 9A, the paddles are arranged infour "V-shaped" rows. The V-shaped rows of paddles serve to eliminatetransverse steering torque on the composter which may be experiencedwith the use of helical rows where one end of the paddle row engages thecomposting material prior to the other. The V-shaped rows are orientedso that the paddles at each end of a row engage the compost materialsimultaneously, eliminating any steering effect resulting from paddleson one end of the drum engaging the compost material before the other.Additionally, the paddles of each V-shaped row are offset from those ofadjacent rows to minimize bypassing of compost material past the drum.In one embodiment, the paddles in each row are spaced at 12" intervals.The corresponding paddles of adjacent rows are offset 3" from oneanother. Offsetting of the paddles in this manner promotes completemixing and aeration since the compost material at every point along theentire length of drum 56 is directly in the path of at least one paddle.

It should be readily understood that more or less rows of paddles anddifferent arrangements of paddles may be used. It is preferred howeverthat left and right paddles 58 and 60 are mounted generally to the leftand right of the center point of the drum respectively, while centerpaddles 62 are mounted along a central portion of the drum. Centerpaddles 62 may also be interspersed with the left and right paddlesalong transition portions of the drum as shown in FIG. 9. Minorvariations in the number and arrangement of center paddles interspersedwith left and right paddles are possible in accordance to the presentinvention.

Each paddle has a base section 64 by which it is pivotably attached tobracket 66, which in turn is welded to drum 56 as shown in detail inFIG. 14. Each paddle is additionally secured in position by a shear pin68 inserted into hole 70. Shear pin 68 serves to release the paddle topivot rearwardly if impacted by a solid object during rotation of drumassembly 22. A deflector plate 71 is attached at a rearward angle to aforward edge of bracket 66. Each paddle includes a cutting edge 72formed on the leading edge of paddle body 74. Extending transverselyfrom the trailing edge of left and right paddles 58 and 60 is a singlepaddle portion 76 extending inwardly toward the longitudinal center ofdrum 56. Center paddles 62 each have a pair of opposed paddle portions78 extending outwardly toward opposite ends of drum 56. The paddleportions are preferably disposed at an angle slightly less thanperpendicular relative to the paddle body.

Each paddle portion 76 serves to generate an air stream directedupwardly of the drum and in the direction of the free end of the paddlewhen the drum is rotated in a direction such that the paddle travelsupwardly and then rearwardly in its circular path around the drum.Stated slightly differently, the normal direction of rotation of thedrum assembly is in the opposite direction of wheel rotation when thecomposter is being driven forward.

Having described the construction of the preferred embodiment, itsoperation will now be explained. The primary function of composter 10 isto shred, mix and aerate solid composting material. While a wide rangeof materials can be accommodated, the preferred embodiment isparticularly suited to the composting of relatively light agriculturalwastes such as straw and grass.

Referring now to FIGS. 4 and 6, to configure the composter for beingdriven sideways, each hydraulic cylinder 43 is activated to lower frame12 onto the ground and to raise each wheel several inches above theground. Tail section 31 is retracted to its raised stowed position byhydraulic cylinder 54. Each frame assembly 40 is pivoted to itstransverse position as shown in FIG. 6; left and right drive wheels 14and 16 are thereby aligned transversely, as are left and right rearcaster wheels. Left drive wheel 14 is then drivably disengaged from leftdrive motor 50 by pushing T-handle 78 inward to disengage the planetarygear drive as discussed above. Each hydraulic cylinder 43 is thenactivated to lower each wheel and raise frame 12 above the ground.Composter 10 is now configured for being driven sideways. It ispropelled in this configuration by right drive wheel 16, now facing inthe direction of "forward travel", which by virtue of being fitted withflexible hydraulic supply and return lines is operable in the transverseposition. Steering is accomplished by operation of hydraulic cylinder 45to "swing" right drive wheel 16 slightly as required to adjust thedirection of travel. After arriving at the desired location, thecomposter is reconfigured to its composting mode by reversing theforegoing procedure.

If it is necessary to transport the composter a greater distance, othertransporting configurations are provided which allow the composter to beflat-towed by a truck. Referring to FIGS. 3 and 4, each wheel is raisedabove the ground, pivoted to its transverse position, and the wheelslowered, raising frame 12 above the ground. Left drive wheel 14 isdrivably disengaged as before, and left rear castor is locked againstcastoring action by pin assembly 19. As best seen in FIG.7, a pair ofauxiliary towing wheel assemblies 80a and 80b are then mounted on theright side of frame 12 by being inserted into channels 82a and 82b, andyokes 84a and 84b respectively, and secured therein by locking pins 86.Auxiliary towing wheel assemblies 80a and 80b are additionally securedby lateral link 86 which is pinned into bracket 88 and frame 12 asshown. Right side drive wheel 16 and right rear castor 20 are thenraised to lower the right side of frame 12 onto towing wheel assemblies80a and 80b. As shown in FIG. 2, fifth-wheel assembly 90 is anarticulated, hinged frame assembly which is normally stored in aretracted position, and which is extended and locked into position asshown in FIG. 7 for being hooked to a truck (not shown) for towingcomposter 10. Fifth-wheel assembly 90 may be raised and lowered by anysuitable winch assembly 92 (FIG. 6). An alternative fifth-wheel designis shown in FIG. 7A where rather than a separate towing wheelassemblies, an integral rear towing wheel assembly 81 is provided whichcan be raised into and lowered from its retracted position (FIG. 7A) byoperation of hydraulic cylinder 83 without being detached from frame 12.Composter 10 thus configured may be conveniently towed over public roadswith considerably less expenditure of time, effort and expense whencompared to prior art composters. Towing the composter is furtheraccommodated by the novel frame design of the present invention as shownin the figures. Drum 56 serves as a tension member interconnectingvertical subframes 12a and 12b as discussed above. The use of drum 56 asa tension member in frame 12 eliminates the need for additionalstructural members to resist spreading forces exerted on subframes 12aand 12b during operation and towing. Frame 12 can therefore be designedwith a lower overall height to accommodate passage beneath lower bridgesand overpasses. Upon arriving at its destination, towing wheelassemblies 80a and 80b are removed and composter is reconfigured foroperation by reversing the above procedure. In the alternativeembodiment, wheel assembly 81 is retracted by operation of hydrauliccylinder 83.

While suitable for use with various composting materials, the preferredembodiment of the present invention is of particular value in thetreatment of relatively light composting materials such as straw orgrass wastes. Prior art composters have proven generally unsatisfactoryfor processing such wastes due to their inability to effect adequateaeration of the materials to ensure aerobic conditions throughout thematerial, and due to their inability to effect adequate removal ofexcess moisture from the material when required. Applicants havediscovered a solution to these problems in the form of the presentinvention wherein a novel drum and paddle assembly 22 is rotated at highspeed in a direction opposite to that of prior art composters. Inaddition to directly impacting the composting material for shredding it,the rotating drum assembly 22 also draws air from ahead of the composterinto chamber 24 and generates a high-speed stream of air in chamber 24.The high speed air stream entrains the relatively light materials andcirculates them in overlapping, counter-rotating circular patternswithin chamber 24 for thoroughly aerating and mixing them. The entrainedmaterials are suspended and circulated in the air streams, and thenredeposited in a windrow to the rear of the rotating drum. As a furtheradvantage, after mixing and aerating the composting materials asdescribed, the present invention redeposits the materials in arelatively tall, more squared-off windrow having a higher volume ofmaterials per unit of surface area than known composters.

To begin a composting operation, engine 38 is started, and drum drivemotors 48a and 48b are engaged to counter-rotate drum assembly 22,preferably at approximately 550 RPMs. Composter 10 is now raised orlowered to a desired ground clearance by activation of hydrauliccylinders 43. By so doing, composter 10 can be adjusted to process moreor less material. This unique ability of the present invention allowsfor a more efficient composting operation by permitting greater volumesof material to be formed into a single windrow and processed in a singlepass, resulting in more efficient use of the available ground area, andless processing time for a given amount of material. The heightadjusting ability is additionally useful in that as the compostingprocess partially decomposes the windrow of material, the volume ofmaterial decreases. The present invention allows the operator to readilyadjust for the volume decrease without any decrease in the effectivenessof mixing and aeration.

Having selected the appropriate height, the operator now drivescomposter 10 forward to engage the composting material. As the composterengages and proceeds along the windrow, the composting material is mixedand aerated by the action of the counter-rotating drum assembly. Wedefine counter-rotation to mean rotation in a counterclockwise directionwhen viewed from the right end of the drum assembly, or stated slightlydifferently, in the opposite direction of rotation of forward rollingdrive wheels 14 and 16. Counter-rotating drum assembly draws air intochamber 24 from ahead of the composter in the form of an upwardly andrearwardly directed air stream ahead of the drum assembly, providingsignificant advantages as will be further explained. As composter 10approaches, the upwardly flowing air stream first engages the windrowahead of the drum assembly and entrains a portion of the material whichtravels in the air stream and which does not directly engage thecounter-rotating drum assembly. Counter-rotating drum assembly 22 thenengages the remaining material which is deflected by deflector plate 71toward cutting edge 72, where the material is shredded, and thenentrained in the air stream. While the precise amounts of materialshredded in each pass of the composter are not known with certainty, inthe processing of grass straw, for example, 3-4 passes through thecomposting material will normally produce a thoroughly shreddedcomposting material.

Under certain operating conditions, particularly when processing heaviermaterials, drum 30 can be slowed and even stalled. Owing to thehydraulic coupling between the drum and engine, stalling of the drum canstall the engine as well. In the preferred embodiment, this problem isaddressed by monitoring the engine speed to detect slowing of the drum,and reducing power to the drive wheels when slowing of the drum isdetected. Reducing power to the drive wheels slows the forward progressof the composter through the windrow, thereby reducing the load on thedrum and allowing it to resume its normal operating speed. In thepreferred embodiment, the power to the drive wheels is first reduced byto 50% or normal, and if after no more than a few seconds the drum hasnot resumed its normal operating speed, further reducing power to thedrive wheels to 30% of normal. Once the drum has resumed normaloperating speed, the power to the drive wheels is increased to itsnormal level. In order to avoid lurching and resultant damage to thedrive mechanism, applicants have found that the power to the drivewheels must be resumed gradually rather than all at once.

Reducing and increasing the power to the drive wheels in response tochanges in the drum speed is achieved by means of electrical control ofthe hydraulic pumps which provide pressurized hydraulic fluid to theleft and right drive wheel hydraulic motors 42a and 42b respectively. Aschematic diagram of the control system is shown in FIG. 16. A manuallyoperated speed controller is provided for each of the two drive wheels.During normal operation, speed controllers 104a and 104b electricallycontrol the output of hydraulic pumps 40a and 40b responsive to movementof the speed controllers by the operator. When drum 30 (not shown inFIG. 16) slows, a corresponding slowing of alternator 102 triggers asignal to controller 100, a Sundstrand Model MCH22BL1844. In response,controller 100 reduces the voltage applied to speed controllers 104a and104b by 50%, which reduces the power to left and right drive wheelhydraulic motors 50a and 50b respectively by a corresponding amount. Ifwithin two seconds drum 30 has not resumed its normal operating speed,controller 100 further reduces the voltage to speed controllers 104a and104b to 30% of normal. In applicants' experience reduction of power tothe drive wheels to 30% of normal has been sufficient to overcome allbut the most severe stalling conditions.

Once drum 30 has resumed its normal operating speed, controller 100restores normal voltage to speed controllers 104a and 104b and normaloperation is resumed. Applicants have found that the control system asdescribed is so responsive that it is necessary to resume normal powerto the drive wheels gradually in order to avoid lurching of thecomposter and damage to the drive train. To that end, once the drum hasresumed normal operating speed controller 100 increases the voltage tospeed controllers 104a and 104b gradually over several seconds.

The entrained composting material is propelled upwardly and rearwardlyin a pair of generally rotating vortex-like airstreams. The end paddlesgenerate air currents directed upwardly of the drum and transverselytoward the center portion of the drum, while the center paddles generatean air current directed upwardly and rearwardly of, and transverselytoward the ends of the drum when the drum is rotated. The air currentsgenerated by the end and center paddles intersect and combine to formthe vortex-like, compost entraining air stream for mixing and aeratingthe windrow of composting material.

The airstreams overlap at their inner portions, providing repeatedexchange of entrained material therebetween. As the air streams begin tolose their velocity, the composting material begins to drop out of theair stream and is redeposited into a windrow. Applicants have discoveredfor the first time that this method of composting relatively lightcomposting materials such as straw and grass wastes solves theaforementioned shortcomings of prior art composters; namely, that isthat the relatively light wastes of this nature can be sufficientlyaerated, mixed and dried as necessary by being entrained in andcontacted with a relatively large volume air drawn into a mixing chamberby a drum and paddle design according to the present invention.

The airstreams are generated according to the preferred embodiment bythe left, right and center paddles previously described. As best seen inFIG. 9 and 14, each row of paddles according to the present inventionincludes a group of paddles having paddle portions 76 facing towardopposite ends of the drum. As the drum is rotated , each paddle portion76 draws air into chamber 24 and generates a series of airstreamsflowing in the direction of the drum rotation and laterally outwardlytoward the end of the drum. The series of airstreams generated by thetwo group of similarly oriented paddle portions 76 combine to formoppositely rotating airstreams spiralling rearwardly within chamber 24and intersect. The interspersing of paddles having opposite facingpaddle portions 76 near the center of the drum creates a region in whichthe oppositely rotating airstreams overlap. In the overlapping region,composting material is continuously exchanged between the airstreams,providing more thorough mixing of the composting materials than hasheretofore been possible. The relatively light materials remainentrained in the airstreams for a relatively long time, until the airstream slows sufficiently to cause the material to fall from theairstream. In this way, the composting material is afforded an extendedcontact time for aeration and drying. As the airstreams spiral rearward,they exit chamber 24 through rear opening 27 and rear tail portion 31.Rear drapes 35 serve to limit the rearward travel of the airstreams andany entrained or thrown composting materials. Applicants have discoveredthat the mixing and aerating effectiveness of the present invention issignificantly enhanced by the use of tail section 31, which apparentlyserves to promote the formation and rearward extension of the rotatingairstreams, extending the contact time between the air and compostingmaterials. The ability of the present invention to provide extended,interstitial aeration of relatively light composting materials has notbeen possible with prior art composters, and represents a significantadvance in the art.

A further benefit of the present invention over prior art composters isrelated to the large volume of fresh air which is continually drawn intochamber 24 and into intimate contact with the composting material. Thisfeature is also of significant benefit when composting heavier materialswhich may not be readily entrained in the airstream, and which are mixedprimarily by being thrown upwardly and rearwardly due to contact withpaddle portions 76. Even so, with the large amount of air drawn intochamber 24 in the form of high-speed air streams, these heaviermaterials are contacted with significantly more air under more effectiveaerating conditions than is possible with known composters.

Having illustrated and described the principles of my invention in apreferred embodiment thereof, it should be readily apparent to thoseskilled in the art that the invention can be modified in arrangement anddetail without departing from such principles. I claim all modificationscoming within the spirit and scope of the accompanying claims.

We claim:
 1. A drum and paddle assembly for mixing and aerating awindrow of composting material comprising:a. an elongate drum having alongitudinal axis, first and second end portions, and a center portion,the drum being rotatable about its longitudinal axis at a predeterminedrotational speed; and b. means extending outwardly from the drum forgenerating a compost entraining air stream when the drum is rotated atthe predetermined speed, the compost entraining air stream having asufficient velocity for entraining substantially all of the compostingmaterial therein for mixing and aerating the windrow of compostingmaterial when the rotating drum is engaged therewith.
 2. A drum andpaddle assembly according to claim 1 wherein the compost entraining airstream comprises a plurality of air currents, and wherein the aircurrent generating means comprises a plurality of paddles extendingoutwardly from the cylindrical outer surface of the drum, each saidpaddle comprising a base portion connected to the drum, and a bladeportion, each said blade portion having a major surface oriented forgenerating at least one said air current having a sufficient velocityfor entraining and transporting composting material upwardly of therotating drum when the drum is rotated at the predetermined rotationalvelocity.
 3. A drum and paddle assembly according to claim 1 wherein thecompost entraining air stream comprises a plurality of intersecting aircurrents, each said intersecting air current having a sufficientvelocity for entraining and transporting a portion of the windrow ofcomposting material upwardly of the drum, and transversely relative tothe drum when the drum is rotated at the predetermined rotationalvelocity.
 4. A drum and paddle assembly according to claim 3 wherein themeans for generating a plurality of intersecting air currentscomprises:a plurality of end paddles extending radially outwardly fromthe first and second end portions of the drum, each said end paddlecomprising a base portion connected to the drum and a blade portion, theblade portion having a major surface oriented relative to the drum forgenerating an air current directed upwardly of the drum and transverselytoward the center portion of the drum when the drum is rotated at thepredetermined rotational speed; a plurality of center paddles extendingradially outwardly from the center portion of the cylindrical outersurface, each said center paddle comprising a base portion connected tothe drum, and a blade portion having first and second major surfaces,said first and second major surfaces oriented relative to the drum forgenerating an air current directed upwardly and rearwardly of, andtransversely toward the first and second end portions of the drumrespectively when the drum is rotated at the predetermined rotationalspeed; and the air currents generated by said end and center paddlesintersecting and combining to form the compost entraining air stream formixing and aerating the windrow of composting material when the rotatingdrum is engaged therewith.
 5. A drum and paddle assembly according toclaim 4 wherein said compost entraining air stream comprises avortex-type air stream which transports the entrained compostingmaterial in a generally circular path.
 6. A drum and paddle assemblyaccording to claim 4 wherein said end and center paddles extendingradially outwardly from said drum are arranged in a plurality of helicallongitudinal rows.
 7. A drum and paddle assembly according to claim 4wherein said drum further comprises first and second transition portionsdisposed be%ween the center portion and the first and second endportions respectively, the first and second transition portions of thedrums having a plurality of end paddles and a plurality of centerpaddles extending radially outwardly therefrom.
 8. A drum and paddleassembly according to claim 1 which further comprises means forcomminuting said composting material.
 9. A drum and paddle assemblyaccording to claim 8 wherein said means for comminuting said compostmaterial includes a blade extending radially outwardly from said drumfor engaging and cutting said composting material when said drum isrotated.
 10. A compost aerating apparatus for mixing and aerating awindrow of composting material comprising:a. a frame having a front, arear, and first and second opposing sides; b. driving means connected tothe frame for propelling the apparatus along the windrow; c. a pair ofrear wheels rotatably connected to the frame; d. an elongate cylindricaldrum journaled transversely in the frame, the drum having a longitudinalaxis, first and second end portions and a center portion; e. meansdrivably connected to the drum for rotating the drum at a predeterminedrotational speed; and f. the drum including means for generating acompost entraining air stream when the drum is rotated at thepredetermined speed, the compost entraining air stream having asufficient velocity for entraining substantially all of said compostingmaterial therein for mixing and aerating the windrow of compostingmaterial.
 11. A compost aerating apparatus according to claim 10 whereinthe compost entraining air stream comprises a plurality of air currents,and wherein the means for generating said entraining air streamcomprises a plurality of paddles extending radially from the cylindricalouter surface, each said paddle comprising a base portion connected tothe drum and a blade portion, each said blade portion having a majorsurface oriented for generating an air current having a sufficientvelocity for entraining and transporting a portion of the windrow ofcomposting material upwardly of the drum when the drum is rotated at thepredetermined rotational velocity.
 12. A compost aerating apparatusaccording to claim 11 wherein the means for generating the plurality ofintersecting air currents comprises:a plurality of end paddles extendingradially outwardly from the first and second end portions of thecylindrical outer surface of the drum, each said end paddle comprising abase portion connected to the drum and a blade portion, the bladeportion having a major surface oriented relative to the rotationaldirection of the drum for generating an air current flowing upwardly ofthe drum and transversely toward the center portion of the drum; aplurality of center paddles extending radially outwardly from the centerportion of the drum, each center paddle comprising a base portionconnected to the drum and a blade portion having first and second majorsurfaces, said first and second major surfaces oriented relative to thedrum for generating an air current flowing upwardly of the drum, andtransversely outwardly toward the first and second end portions of thedrum respectively; and the upwardly and transversely flowing aircurrents generated by the end paddles and the center paddlesintersecting and combining to form the compost entraining air stream formixing and aerating the composting material.
 13. A compost aeratingapparatus according to claim 12 wherein said compost entraining airstream comprises a vortex-type air stream which transports the entrainedcomposting material in a generally curved path.
 14. A compost aeratingapparatus according to claim 13 wherein said end and center paddlesextending radially outwardly from the drum are arranged in 4 helicallongitudinal rows on the drum, each helical longitudinal row traversing90° circumferentially around the outer surface of the drum.
 15. Acompost aerating apparatus according to claim 13 wherein said drumfurther comprises first and second transition portions disposed betweenthe center portion and the first and second end portions respectively,the first and second transition portions of the drums having a pluralityof end paddles and a plurality of center paddles extending radiallyoutwardly therefrom.
 16. A compost aerating apparatus according to claim12 wherein said end and center paddles extending radially outwardly fromsaid drum are arranged in a plurality of helical longitudinal rows onthe drum.
 17. A compost aerating apparatus according to claim 12 whereinsaid paddles extending radially outwardly from said drum are arranged ina plurality of V-shaped longitudinal rows.
 18. A compost aeratingapparatus according to claim 10 wherein the compost entraining airstream comprises a plurality of intersecting air currents, each saidintersecting air current having a sufficient velocity for entraining andtransporting a portion of the windrow of composting material upwardly ofthe drum, and transversely relative to the drum for mixing and aeratingthe windrow of composting material.
 19. A compost aerating apparatusaccording to claim 10 wherein said apparatus driving means comprises:apair of drive wheels, one said drive wheel rotatably connected to eachsaid side of the frame; a hydraulic motor drivingly connected to eachsaid drive wheel; a hydraulic pump operatively connected to each saiddrive wheel hydraulic motor for providing a flow of pressurized fluidthereto; and drive control means communicating with each said hydraulicpump for controlling said pressurized fluid flow to each said drivewheel hydraulic motor, each said drive wheel being reversibly drivableindependent of the other for propelling and steering said apparatus. 20.A compost aerating apparatus according to claim 19 wherein said drumdriving means comprises a hydraulic pump and a hydraulic motoroperatively connected thereto.
 21. A compost aerating apparatusaccording to claim 19 further comprising:four drive wheels, two saiddrive wheels rotatably connected to each said side of the frame; ahydraulic motor drivingly connected to each said drive wheel; ahydraulic pump operatively connected to each said drive wheel hydraulicmotor for providing a flow of pressurized fluid thereto; and drivecontrol means communicating with each said hydraulic pump forcontrolling said pressurized fluid flow to each said drive wheelhydraulic motor, each said drive wheel being reversibly drivableindependent of the other for propelling and steering said apparatus. 22.A compost aerating apparatus according to claim 10 wherein said meansfor generating a compost entraining air stream is adapted for generatinga generally upwardly and transversely directed compost entraining airstream ahead of the drum as the compost aerating apparatus is propelledalong the windrow.
 23. A compost aerating apparatus according to claim10 further comprising means for propelling said apparatus sideways. 24.A compost aerating apparatus according to claim 23 wherein said meansfor propelling said apparatus sideways comprises said drive wheels beingpivotably mounted on said frame, said drive wheels being pivotable to aselectable transverse driving position for propelling said apparatussideways, and further comprising said rear wheels being pivotablymounted on said frame, said rear wheels being pivotable to a transverseposition.
 25. A compost aerating apparatus according to claim 10 whichfurther comprises means for towing said apparatus.
 26. A compostaerating apparatus according to claim 25 wherein said meanscomprises;means for supporting a first end of said compost aeratingapparatus; means for retracting said drive wheels and said rear wheelsto respective raised positions above an underlying surface; a dolly;means for removably connecting said dolly to second end of said framefor supporting a second end of said compost aerating apparatus with saiddrive and rear wheels above an underlying surface.
 27. A compostaerating apparatus according to claim 26 wherein said means forretracting said drive wheels and said rear wheels comprises said drivewheels and said rear wheels being pivotably mounted on said frame, saiddrive wheels and said rear wheels being pivotable to respectivepositions between planes coincident with the front and rear of saidframe.
 28. A compost aerating apparatus according to claim 25 whereinsaid towing means comprises an extendable frame for removably engaging afirst end of the compost aerating apparatus to a truck, and furthercomprises retractable towing wheels connected to said frame forsupporting a second end of said apparatus while being towed.
 29. Acompost aerating apparatus according to claim 10 which further comprisessurfaces defining a chamber for containing said entraining air stream.30. A compost aerating apparatus according to claim 29 which furthercomprises means for forming a windrow of mixed and aerated compostingmaterial discharged from said entraining air stream.
 31. A compostaerating apparatus according to claim 30 wherein said air streamcontaining chamber and said windrow forming means comprise a transversetop wall disposed above said drum, said top wall having a width lessthan the length of said drum, and which further comprise a pair ofopposed sidewalls joined at their respective upper ends to opposite endsof said top wall, each said sidewall having an angled upper sidewallportion extending downwardly and outwardly from the respective ends ofsaid top wall, and a lower sidewall portion extending substantiallyvertically downwardly from said angled upper portion.
 32. A compostaerating apparatus according to claim 31 wherein said drum is disposedbetween said opposed sidewall lower portions.
 33. A compost aeratingapparatus according to claim 31 which further comprises an air inletopening formed in one or more of said opposed side walls.
 34. A compostaerating apparatus according to claim 31 wherein said air streamcontaining chamber further comprises a front wall and an air inletopening formed in said front wall.
 35. A compost aerating apparatusaccording to claim 31 wherein said air stream containing chamber andsaid windrow forming means includes an extended chamber portioncomprising an upper surface, a pair of opposed side surfaces, and adownwardly depending end surface.
 36. A compost aerating apparatusaccording to claim 35 wherein said pair of opposed side surfaces anddownwardly depending end surface each comprises a sheet formed of aresilient material.
 37. A compost aerating apparatus according to claim35 wherein said extended chamber portion is operable between a first,extended position and a second retracted position.
 38. A drum and paddleassembly according to claim 10 which further comprises means forcomminuting said composting material.
 39. A drum and paddle assemblyaccording to claim 38 wherein said means for comminuting said compostmaterial includes a blade mounted on said drum, the blade including acutting surface for cutting said composting material when said drum isrotated.
 40. A compost aerating apparatus according to claim 10 whereinsaid first and second drum end portions are journaled in respectivefirst and second opposing frame sides, said first and second endportions being interlockingly engaged with said respective first andsecond opposed frame sides and adapted for resisting a force acting tospread said respective first and second frame sides.
 41. A compostaerating apparatus according to claim 40 wherein said drum first andsecond end portion each includes a thrust bearing mounted outboard ofthe respective first and second opposing frame side, each thrust bearingadapted for rotatably bearing on an outboard surface of its respectiveframe side to resist a force acting to spread the first and secondopposing frame sides.
 42. An apparatus for mixing and aerating a windrowof material comprising:a frame having a front, a rear, and first andsecond opposed sides; a pair of front wheels rotatably connected to theframe; a pair of rear wheels rotatably connected to the frame; anelongate cylindrical drum journaled transversely in the frame, the drumhaving a longitudinal axis and first and second end portions; meansdrivably connected to the drum for rotating the drum at a predeterminedrotational speed; and, means for interlockingly engaging said first andsecond drum end portions with said respective first and second opposedframe sides and means for transmitting a transverse towing force exertedon said apparatus to said first frame side, through said transversecylinder, and to said second frame side.
 43. A compost aeratingapparatus according to claim 42 wherein said towing force transmittingmeans comprises first and second thrust bearings mounted on said firstand second drum end portions a respectively.